Device for optically measuring light, photometer



June 8 1926.

E. MAYER DEVICE FOR OPTICALLY MEASURING LIGHT PHOTOMETER Filed August 27, 1925 it ti Patented June 8, 1926 "UNITED STATES PATENT OFF ICE.

nun. MAYER, or IENNA, AUSTRIA.

nnvxen FOR OPTICALLY mnasunme LIGHT, rnoroun'rna Application flied August 27, 1928, Serial No. 659,456, and-in Austria April 2-8, 1923.

invention relates to a new and improved exposure meter,

One of the objects of my invention is to provide an exposure meter which will enable the user to readily and directly determine the exposure time and in addition the corresponding diaphragm setting, for a camera provided with a lens and also for enlarging or reproducing appliances embodying lenses, so that proper negatives or positives can be. secured.

Another object of my invention is to provide an exposure meter which can be operated directly for the above mentioned purposes, by means of light which is transmit-v ted, refracted, reflected or is radiated from or emanates in any manner from the object to be photographed or reproduced.

Other objects of my invention will be set forth in the following description and drawshows the transmitting sections used in the second embodiment.

Fig. 5 is a detail view of the second embodiment. I

Fig. 6 illustrates a third embodiment.

In the construction shown in 'Fig. '1, a number of light comparing sections it of gradually vided.

tions may be arranged side by side, although my invention is not limited to any particular arrangement of the said comparing sections. Each of these sections has an identifying mark such as a numeral formed thereon and a light contrast is provided between each section and its identifying numeral, so that the identifying numeral is visible when theproper amount of light is passed through the respective section.-

For example, each of the comparing sections may be translucent and the identifyvarying translucency are promovable cover is is As shown in Fig. 2, these comparing sec.

ing numerals may then be given a black or other contrasting color. If the comparing sections have one of their faces given a black color then the identifying numerals can be rendered visible bysimply omitting the black coloration at the part of each said fsection corresponding to the outline of the identifying numeral.

These comparing sections are held in position between two transparent panes 9 made of glass or any other suitable material which is permeable to light. Of course, the comparing sections can be directly formed upon a sheet of glass of va ing thickness so as to provide the requisite ifl'erence in light permeability. The comparing sections are mounted at the top of a tube 0 which is provided with an ordinary iris diaphragm c. This diaphragm c is actuated by a ring m which can be manipulated on the outside of the tube so as to open or close the diaphragm.

I have not shown the details of construction of the iris diaphragm c as this in itself is a well known piece of apparatus.

An indicator can be provided upon the ring at to 00-0 rate with any ordinary and well known sea e, so that the extent to which the diaphragm is opened can be readily determined.

A sheet of ground glass or other material z is located in front of the diaphragm 0 so that the formation of an image within the apparatus is prevented when a diaphragm opening is very narrow. The tube 0 on which thecomparing sections, the iris diaphragm and the outer sheet 2' are mounted, 1s slidably mounted within an outer tube at provided with an ordinary magnifying lens I). The usual flaring end a is provided so as to protect the eye of the observer from external. light. y

In the embodiment shown in Fi 1, a rerovided for t e end of the inner tube e an this tube contains two sheets 8 made of glass or othertransparent material between whichmenibers of varying light permeability can be located. This is foril the purpose of subduing very bright li t.

In the embodiment shown in Figs. 3, 4 and 5, an inner tube n is located within the tube c. Any desired portion of the inner end of the inner tube n can be covered by an inner opaque covering member 0, which in this embodiment'is shown as semi-circular, so that it covers half the aperture of the said inner n Elssusn l tube n. The tube 92 can be turned by means of a handle 12 which passes through a slot in the tube e. In this embodiment there are four comparing sections 72. which are arranged as shown in Fig. 4, and as the inner tube 71. is turned by means of the handle p, .the observer can excludefrom the field of vision any of the sections k.

In the embodiment'shown in Fig. 6 the magnifying lens is omitted and a tube 01 of any suitable length is provided in which another tube e is slidably mounted. The light comparing sections can be provided by means of a translucent wedge 0' provided with identifyin numerals for adjacent zones thereof. hese adjacent zones are of different light permeability due to the difference in thickness of the wedge at various portions for example, the comparing section or field identified by the numeral 1/10 is the least permeable to light. Hence, this numeral 1/10, for example, can only be observed when the light passing through this section to its in corresponds to sunlight or the like. If such light conditions are not present, then the numeral 1/ 10 cannot be seen by the observer. The section or field identified by the numeral 1/5 is somewhat more light permeable from the first mentioned section, so that the numeral 1/5 can be seen by the observer when sunli ht is not available. Similarly, the numera 5 identifies a section which is more light permeable than the second mentioned field, and the field identified by the numeral 20 has a still greater light permeability.

The same relationship exists in the embodiment shown in Figs. 1 and 2.

In the embodiment shown' in Figs. 3-5, for examplle, when the diaphragm is opened est extent, the light emanating from the object to be photographed, or emanating from the picture or image which is to be reproduced, is perceptible because said light renders one of the sections visible. The observer will see only the numerals on those sections which are sufiiciently illuminated by the said light, whose intensity varies according to the conditions present- For example, if the amount of light transmitted is such that the observer can see the numeral 1/5, he will not be able to see the numeral 1/10, and he will be able to see the numemls 5 and 20. The numeral 1/5, namely the numeral corres nding tothe field having :the greatest lig t permeability, will identify to the observer the light conditions which are present.

The iris diaphragm is then closed to its greatest extent and is then opened until the observer can just see the identifying numeral which corresponds to the light conditions present. The aperture of the iris diaphragm which can be readily indicated by means of a suitable scale, for example, and the identifying numeral. which indicates directly "to-the observer the. light conditions which are present, enable him to immediately determine the amount of light which is necessary for securing the corresponding negative or positive.

For example, the identifying numeral for the field of greatest light permeability can correspond to the time of exposure and the diaphragm setting can correspond to the diaphragm setting on the camera or other optical apparatus which is being used. The user can secure the proper combination of exposure time and diaphr setting, which regulates the amount 6f light acting upon the sensitive plate, by either adjusting the shutter opening or the diaphragm setting for the lens which is being used. In man cases the diaphra setting can be immediately adjusted with respect to the shutter opening or. aperture so that the sensitive plate is acted upon'by the pro er amount of light so as to clearly re rodhce all the objects within the field of t e lens, including those objects which are near the lens and those which are far away from thelens.

I have described a preferred embodiment of my invention, but it is clear that numerous changes and omissions could be made without departing from its spirit.

I claim 1. In an exposure meter, the combination of a plurality ofi fields of varying light permeability, each of said fields having anidentifying mark thereon, adjustable means for regulating the aperture through which light passes to the said fields, and manuall operated means for excludin selected fiel s from the line of vision of t e observer.

2. A device according to claim 1 in which the said diaphragm.

.3. In an exposure meter, the combination of a plurality of fields of varying light permeability, the said fields having opa ue faces and contrasting light permea le ldentlfying marks formed thereon, means for controlling the aperture through .which' adjustable means consists of an iris light can be caused to pass through the said fields, and manually operated means for excluding selected fields from the line of vision of the observer.

4. In an exposure meter, the combination of a plurality of fields. of varying light permeability and having identifyin marks formed thereon, manually operate means for excluding selected fields from the line of vision of the observer, and additionally manually controlled means for regulating a sheet of translucent material ascciated the aperture through which light passes to with the said diaphragm and adapted to the said fields. prevent the formation of an image in the 5. In an exposure meter, the combination device when the diaphragm opening is small,

5 of a plurality of fields of varying light and manually 0 erated means for exclud 1L5 permeability, each of said fields having an ing selected fiel s from the line of vision identifying mark thereon, an iris diaphragm of the observer. associated with the said fields and adapted In testimony whereof I have signed my to control the size of the aperture through name to this specification.

19 which light can pass through the said fields, DR. EMIL MAYER. 

